Modern West European languages (and their offshoots such as American English) generally have just one voiceless fortis sibilant phoneme /s/, whatever else there may be, such as /z, š, θ , c/. But in every considerable area at least two quite different [s] phones are in use, dorsal [ s ] and apical [ṣ]. The commoner variety is the dorsal [ s ]. In its articulation the tongue tip is idle (in persons with a ‘normal bite,‘ as the dentists say, the tip touches the lower incisors or gums or both), and the sibilant squeeze is made against the upper alveolar ridge by the upper surface of the tongue. The apical [ṣ] is nowhere truly rare, but it is the less common variety in the principal areas, except that it is standard in Castilian Spanish. The apical articulation has the tongue tip raised, and the tip itself makes the sibilant squeeze.
No takes yet. Share an insight, caveat, or question.
Martin Joos (1952) studied this question.